Used for detection of pneumococcus. Polyvalent anticapsular antibodies are mixed with the bacteria, and then the mixture is examined microscopically. A greater refractiveness around the bacteria is a positive reaction for S. pneumoniae.

Use of optochin.

Differentiation of S. pneumoniae from viridans strep. Viridans and enterococci are optochin resistant.

Differentiation of S. pneumoniae from other alpha-hemolytic strep.

Bile solubility - S. pneumoniae lyse in bile, while others do not. Also: pneumococci are sensitive to optochin, where others are not.